Narrow-aisle lift truck



June 19, 1962 w. M. SHAFFER NARROW-AISLE LIFT TRUCK 7 Sheets-Sheet 1 Filed March 9, 1961 M3 gay .6 mix mwwm MW 3? y ,3 a

June 19, 1962 w. M. SHAFFER 3,039,638

NARROW-AISLE LIFT TRUCK Filed March 9, 1961 7 Sheets-Sheet 2 pa /5K m/zwg mee/A/arm/ J ITJ M MW June 19, 1962 w. M. SHAFFER 3,03 38 NARROW-AISLE LIFT TRUCK 7 Sheets-Sheet 3 Filed March 9, 1961 June 19, 1962 w. M. SHAFFER 3,039,638

NARROW-AISLE LIFT TRUCK Filed March 9, 1961 7 Sheets-Sheet 4 INVENTOR.

June 19, 1962 W.M. SHAFFER NARROW-AISLE LIFT TRUCK 7 Sheets-Sheet 5 Filed March 9, 1961 M m a i 2% My n2 P M A a f MW MM f? June 19, 1962 w. M. SHAFFER NARROW-AISLE LIFT TRUCK '7 Sheets-Sheet 6 Filed March 9, 1961 illilj MWQ Jmd/U, y

United States Ohio Filed Mar. 9, 1961, Ser. No. 94,531 15 Claims. (Q1. 214-730) This invention relates to lift trucks and more particu larly to a narrow aisle lift truck characterized by a drive axle assembly including a mast and fork which may be turned from a position transversely of the lift truck to a position aligned with the central axis of the lift truck to facilitate stacking of loads in a narrow aisle. Lift trucks of this type permit the use of narrow aisles: and result in allowing more than 35% more material being put into a warehouse.

This invention relates to lift trucks of the type shown and described in my co-pending application Narrow Aisle Warehousing Lift Truck, Serial No. 698,663, filed November 25, 1957, now Patent No. 2,986,295, (Do ket No, -458) of which the instant application is a continuation-in-part and the hyd-aulic drive of the instant application is also characterized by components corresponding to those disclosed and claimed in my co-pending application Hydraulic Drive for Lift Truck, Serial No. 849,588, filed October 29, 1959 (Docket No. 5908) of which the instant application is a continuation-in-part.

It is among the objects of the instant invention to provide a lift truck having a frame which is characterized by a relatively wide rear portion which supports the power unit and wherein the rear portion of the frame is supported by dirigible wheels and the forward part of the frame is characterized by an elongated narrow central portion which has pivoted at its outer end a transverse drive axle. The mast and lifting fork assembly is carried by the front drive axle and means are provided to swing the drive axle from its normal position transversely of the frame to a position wherein the drive axle is aligned with the central axis running longitudinally of the frame. This arrangement results in the lifting forks and the load carried thereby to be at right angles to the lift truck. To provide stability for such sharp turning and to guide the lift truck as loads are being stacked by the lift truck, Outriggers are arranged so that when extended they are aligned with one of the dirigible wheels.

One of the results of the construction provided is that when an outrigger is swung to one side of the lift truck, it raises that side of the lift truck so as to raise the dirigible wheel nearest the extended outrigger away from the floor and, at the same time, the dirigible wheel at the opposite side of the lift truck is aligned with the wheel on the extended outrigger so that the eifective width of the lift truck is greatly increased and stability against overturning due to the eccentric position of the load is provided.

It is among the objects of my invention to provide a lift truck as described in the preceding paragraphs wherein the mounting of the drive axle on the narrow frame extension provides a space at each side of the lift truck and wherein the outriggers may be swung into this space for storage when the drive axle is transversely of the vehicle. When an outrigger is extended at the left-hand side of the vehicle, then the drive axle may be turned so as to swing into this space at the left-hand side of the vehicle. Conversely, when the right-hand outrigger is extended, the drive axle may be turned so as to move through the right-hand space vacated by the right-hand outrigger.

It is a further object of my invention to provide a lift truck according to the two preceding objects wherein atent the lift truck is provided with a conventional steering wheel for the operator and the steering linkage is connected to the dirigible wheels for normal steering of the vehicle with the lifting forks forwardly of the vehicle and the drive axle transversely of the vehicle and wherein linkage is provided which operatively connects the outriggers to the dirigible wheels so as to maintain the dirigible wheel at one side of the vehicle in alignment with an outrigger wheel at the opposite side of the vehicle.

It is a further object of my invention to provide a lift truck according to the preceding object wherein the outriggers when swung to storage position in said space at each side of the vehicle, the outer free ends of said Outriggers are in engagement with means carried by the drive axle so that the drive axle may not be turned from its position transversely of the vehicle when the outriggers are both in storage position.

It is a further object of my invention to provide a lift truck according to the preceding objects wherein swinging of one outrigger from its storage position to an extended position disengages said outrigger with respect to the drive axle so that the drive axle may be turned through the space on the same side of the vehicle as said extended outrigger, but is prevented from being swung in an opposite direction by the other outrigger which is maintained in storage position.

It is a further object of my invention to provide a lift truck according to the preceding objects wherein the lift truck is provided with a power unit such as an internal combustion engine having an ignition circuit wherein the outriggers and the front drive axle are operatively arranged with respect to switches in said ignition circuit so that the operation of the power unit is interrupted upon movement of the axle and Outriggers toward an unsafe position so that a safety interlock is provided between the power unit and the manipulation of the drive axle and Outriggers.

It is a further object of my invention to provide a hydraulic drive mechanism for a lift truck according to the preceding objects wherein the power unit is arranged to drive a pair of gear pumps and wherein the output of the gear pumps is characterized by the one pump being about twice the capacity of the other pump and wherein a tilt-hoist valve is provided for tilting the mast and raising and lowering the carriage or lifting forks and wherein a drive control valve is provided for determining the drive condition of the vehicle, and wherein hydraulic cylinder means are provided for swinging the outriggers and wherein variable displacement hydraulic motors are provided to drive the traction wheels of the vehicle and a multiphase valve is provided for guiding the vehicle for stack ing operations.

Further objects and advantages relating to economies in manufacture, efiiciency and safety in operation, ruggedness of construction and ease of operation and service will appear from the following description and the appended drawings wherein:

FIG. 1 is a perspective view of a lift truck made according to my invention;

FIG. 2 is a plan view with parts in section showing the linkage between the dirigible wheels, the outriggers and the drive axle;

FIG. 3 is an elevation with parts in section taken as indicated by the plane 33 of FIG. 2;

FIG. 4 is an elevation with parts in section taken as indicated by the plane 44 of FIG. 2;

FIG. 5 is an end elevation of the dirigible wheel mounting taken as indicated by the plane 5-5 of FIG. 2;

FIG. 6 is a view taken from the rear of the lift truck with the right-hand outrigger extended so as to tilt the vehicle slightly and raise the right-hand dirigible wheel from the floor or supporting surface;

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FIG. 7 is a plan view showing the lift truck diagrammatically with the right outrigger extended and the lifting forks swung to the right-hand side of the vehicle;

FIG. 8 is a view similar to FIG. 7 showing the left-hand outrigger extended and the forks turned to the left-hand side of the vehicle;

FIG. 9 is a plan view and wiring diagram showing the interlock between the drive axle, the Outriggers and the ignition circuit for the power unit;

FIG. 10 is a view showing the hydraulic system for tilting the mast, hoisting the carriage, swinging the outriggers and providing traction for the vehicle;

FIG. 11 is a sectional view of the multi-phase valve showing the position of the valve parts with the lift truck in conventional forward or reverse drive;

FIG. 12 is a sectional View of the multi-phase valve showing the control plunger of the valve as moved to a position for rotating the front axle of the vehicle by rotating the drive wheels in opposite directions;

FIG. 13 is a sectional view of the multi-phase valve showing the position of the valve plunger for guiding the drive wheels in a stacking operation by rotating the drive wheels in the same direction but at different rates of rotation;

FIG. 14 is a sectional view of the displacement valve for determing the displacement of the drive motors under different modes of operation of the vehicle; and

FIG. 15 is a sectional view of a pilot-operated check valve forming a part of the hydraulic operation and control of the outrigger cylinders.

Referring to the drawings, the lift truck frame is indicated in its entirety as at 6. The rear portion of the frame 6 is considerably wider than the narrow elongated forward portion indicated at 7. The frame portion 7 is arched centrally thereof as shown in FIG. 1 to provide clearance for the traction wheels. Preferably side frame members 8 taper toward the front of the vehicle and terminate in an integrally formed elongated arched neck portion 7 which provides a journal support for a vertical pivot 9 connecting the drive axle assembly to the frame.

The rear portion of the frame preferably includes a counterweight indicated at '10 and a motor housing 11 with the operators seat indicated at :12 above a part of the motor housing. A protective canopy structure indicated at '13 extends laterally over the operator.

The drive axle assembly includes a right-hand traction wheel 15 and a left-hand traction wheel 16-. Beneath the rear portion of the frame the right-hand dirigible wheel 17 is mounted on a spindle 65 and a left-hand dirigible wheel 18 is similarly mounted on spindle 67. Lifting forks 19 and 20 are carried by the carriage 21 which is arranged to slide vertically on the mast assembly 22.

The mast assembly is provided with a hoist cylinder 23 and chains 24 attached to the carriage to raise and lower the carriage and move the mast sections relative to each other. The mast assembly and the load carriage and lifting forks are carried on the front drive axle assembly which is indicated in its entirety as at 25.

By means hereinafter described in detail, the lift truck is adapted to be operated with the forks forwardly of the lift truck as illustrated in FIG. 1 and this is referred to herein as the normal forward operation of the vehicle. When it is desired to manipulate the truck in a narrow aisle, such as would be found in a warehouse, and to handle pallets for stacking with the lift truck, the drive axle 25 is adapted to be turned so as to be in line with the central axis through the vehicle indicated as at 26 in FIGS. 7 and 8. As will be described hereinafter in detail, the drive axle is provided with a pair of hydraulic traction motors which are controlled by the operator so that one traction motor may be operated in a direction opposite the direction of the other traction motor and thus turn the drive axle assembly 25 to the position shown in FIGS. 7nd 8.

It will be observed from FIGS. 1, 2, 7 and 8 that the provision of the narrow forward portion 7 of the frame results in a space being provided at each side of the lift truck and a left-hand outrigger 27 is arranged to swing into the left-hand space indicated at 28. Similarly righthand outrigger 29 is arranged to be swung into the space indicated at 36.

The front axle assembly 25 is provided with a U-shaped frame indicated at 31 which is turned with the drive axle when the drive axle is swung to the position shown in FIGS. 7 and 8. The frame member 31 includes a laterally projecting lug 32 which projects into the space 30. The right-hand outrigger 29 is provided with an outrigger wheel 33 and the outer end of the wheel axle 33a is provided with a lug 34 having a stud 34a which engages the lug 32 on the frame 31. This arrangement, as best show-n in FIG. 2 and FIG. 4, prevents the drive axle from turning about the pivot 9 to the right since the lugs 32 and 34:: are in engagement. The left-hand side of the vehicle includes a similar arrangement wherein a lug 36 carried by frame 31 extends into the space 28 alongside of the traction wheel 16 and there engages a stud 37 carried by member 38 on the axle 3541 of the left-hand outrigger wheel 35. Accordingly it will be understood that when the vehicle is in normal forward drive ooeration and the Outriggers are retracted, as shown in FIGS. 1 and 2, the drive axle assembly cannot be turned to either side of its normal forward drive position.

The right-hand outrigger 27 is pivotally mounted by pivot pin 49 carried in the bracket 41 secured to the transverse frame member 42. The inclination of the pivot pin 40 causes the outer free end of the outrigger to be raised to the position shown in FIGS. 1 and 4 with the wheel 35 elevated with respect to the supporting surface 43. According, when the outrigger 27 is swung into the storage space 28 at the side of the vehicle, it is elevated with respect to the sup-porting surface for the vehicle. Conversely, when the outrigger 29 is swung to an extended position, as shown in FIGS. 6 and 7, the outrigger wheel is brought into engagement with the supporting surface and, as it is brought into engagement with the supporting surface, it is effective to raise that side of the vehicle having an extended outrigger. The raising or tilting of the vehicle by the outrigger is effective to raise the adjacent dirigible wheel away from the supporting surface.

In FIG. 6 the right-hand outrigger wheel 33 has been fully extended by outrigger arm 29 which is effective to raise the dirigible wheel 17 from the supporting surface and bring the axis of the outrigger wheel 33 into alignment with the axis of the dirigible wheel 18. FIG. 7 is a plan view corresponding to the elevation of FIG. 6 and as here shown the axis of the outrigger wheel 33 and the axis of the dirigible wheel 18 are coincident on the line indicated at 45. Operation of the drive wheels 15 and 16 in the same phase of forward rotation brings the load on the forks into stack S in the aisle A. The reduction in aisle width results in more efiicient use of the warehouse floor space. Thus when the outrigger 29 is extended, the effective width of the vehicle corresponds to the distance between the outrigger wheel 33 and the dirigible wheel 18. This provides for stability adjacent the load carried by the lifting forks at the right-hand side of the vehicle. Conversely, swinging of the lefthand outrigger 27 and its wheel 35 brings the outrigger wheel 35 into alignment with the dirigible wheel 17 along the axis indicated at 46 in FIG. 8. This means that dirigible wheel 18 is lifted from the floor by the tilting of the vehicle and stability is provided for the load on the forks at the left-hand side of the vehicle.

The hydraulic means for swinging the outriggers includes the hydraulic cylinders at each side of the vehicle. The cylinder 47 is pivotally carried by the frame bracket 48 and the piston rod 49 extending from the cylinder 47 is pivoted to the outrigger 27 as at 50. The hydraulic cylinders for the outriggers are double-acting cylinders and when hydraulic fluid is introduced into the cylinder at one side of the piston, the piston rod is projected therefrom to extend the outrigger as heretofore described. Upon directing fluid to the other side of the piston, the outrigger is retracted.

At the right-hand side of the vehicle, hydraulic cylinder 51 is provided which is carried by frame bracket 52 and the piston rod 53 is pivoted to the outrigger 29 as at 54. It will be understood that the valves for the hydraulic fluid admitted to the cylinders 47 and 51 are accessible to the operator as illustrated in FIG. 1. A lever 55 controls the valve directing fluid into the left-hand outrigger 2.7 and control lever 56 directs the fluid into the right-hand outrigger 51. Each lever and the valve controlled thereby has three positions, namely, extend outrigger," neutral and retract outrigger.

A steering Wheel 57 is operatively connected to a steering wheel shaft 58 and thence through steering reduction gear 59 to steering arm 60 connected to the steering link 61. The rear end of the link 61 is operatively connected to the depending ball 62 carried by the steering axle assembly 63. The assembly 63 includes a king pin unit 64 for the right-hand dirigible wheel spindle 65. A left-hand king pin unit 66 carried by the assembly 63 and left-hand wheel spindle 67 is carried on the king pin unit 66.

A steering yoke assembly is pivoted on the dirigible wheel frame as at 68. The yoke assembly includes an upper transverse arm 69 having a left-hand depending ball 70 and a right-hand depending ball 71. The yoke assembly includes the sleeve portion 72 which connects the upper arm 69 to the lower arm 73 for joint swinging movement. A tie link 74 connects the ball 75 on the swinging yoke 73 to the ball 76 for the left-hand spindle 67. Similarly the ball 78 carried at the upper side of the yoke "73 is connected by the tie bar 79 to the ball 80 carried by spindle 65. When the operator turns the steering wheel 57, the movement of link 61 is transmitted to the yoke assembly including upper and lower arm 69 and 73, respectively, and the motion of the yoke members is transmitted to the spindles 65-67 for steering the vehicle for normal forward drive.

To turn the dirigible wheels into proper position for alignment with the selected outrigger, a linkage arrangement is provided connecting each outrigger to the dirigible wheel assembly and steering mechanism. A bracket 82 is carried by the frame adjacent the left-hand outrigger pivot 40 and the bracket provides a pivotal mounting as at 83 for the triangular plate 84. A link 85 has one end thereof pivoted as at 86 to the outrigger 27 and the other end thereof pivoted as at $7 to the plate 84. A link 88 is pivoted as at 39 on the triangular plate 84 and extends rearwardly therefrom within a tube 90' which is pivotally mounted on the ball 70 depending from the upper yoke 69 of the steering mechanism.

The link 88 is provided with an enlarged head portion 91 sliding within the tube 90 and accordingly when the yoke 69 is rocked by the normal steering operations of the vehicle in forward drive, the tube 90 will slide to and fro with respect to the rod 88 which remains stationary in space. When, however, the outrigger 27 is extended laterally of the vehicle, the head 9'1 abuts the shoulder at the end of the tube as at 92, thus rocking the yoke 69 and turning the dirigible wheels to bring the right-hand dirigible wheel into alignment with the axis of the lefthand outrigger Wheel.

A similar interconnection is provided between outrigger 29 by means of bracket 9-3, plate 94- and links 95 and 96 moving with respect to the tube 97 connected to the right-hand ball 71 on the yoke 69. It Will be understood that the arrangement is such that for normal forward drive of the vehicle, as illustrated in FIG.-1, the dirigible wheel spindles 65 and 67 are moved freely by the operators manipulation of the steering wheel 57 and such mo.- tion will have no effect on the Outriggers. When, how- 6 ever, the outriggers are extended, the links 88 and 96 are effective to turn the dirigible wheels into alignment with the outrigger wheels.

In accordance with the foregoing description of the mechanical interlock between the Outriggers and the drive axle, the outriggers prevent turning of the drive axle relatively to the vehicle when the Outriggers are in stored position. Extending one outrigger will permit the rotation of the drive axle with respect to the frame about the pivot 9 in a direction toward the extended outrigger.

In the interests of safety, means are provided to prevent the extension of both Outriggers at the same time and to limit the rotation of the drive axle with respect to the frame to the proper positioning of the Outriggers. Preferably an electrical interlock arrangement is provided as shown diagrammatically in FIG. 9. As heretofore described, the hydraulic pumps for moving the various hydraulic components and providing traction are driven by the engine indicated at 150.

The engine 150 includes an ignition system which derives its electrical power from the storage battery 19 1. The negative side of the battery is preferably grounded to the vehicle frame as at 102 and the engine is also grounded to the frame as at 103'. The positive side of the battery leads, by way of line 104, to line 105 connected to one side of a normally open switch 106. The other side of the switch 106 has connected thereto the line 107 leading to junction 108. A line 109 leads from the junction 108 to one side of a normally open switch 110'. The term normally open switc as used herein, means that the switch includes a button as at 111 which is biased outwardly of the switch box and, when moved to its projected position by a spring within the switch box, the circuit is broken within the switch. When, however, the button 111 is depressed, the circuit is completed through the switch.

The switch 106 includes a button 112 which is depressed to close the circuit through the switch by means of the cam 113 integrally formed on the member 31 carried by the drive axle and pivoted with respect to the vertical pivot 9.

It will be understood that in the event the drive axle and the member 3 1 is turned about the pivot 9 in either direction, the button 112 will be projected and the circuit opened in the switch 106.

The hand-operated lever 55 controlling the left-hand outrigger 27 and the lever 56 controlling the right-hand outrigger 29 are arranged with respect to the button 111 so that movement of either lever to the dotted line retract outrigger position will open the circuit through the switch 110; Switches 106 and 110 are arranged to prevent retraction of an outrigger with the front end assembly in a rotated position.

A normally open switch 115' is mounted on the frame of the lift truck so as to be engaged by the inner edge of the outrigger 27 when the outrigger is moved to retracted or storage position as shown in FIG. 9. Similarly, a normally open switch 116 is mounted on the lift truck frame adjacent the outrigger 29 and the circuit through the switch 116 is maintained as long as the outrigger is held in its retracted position. A line 117 leads from the junction lit-8 to the junction 118 on line 119 extending between terminals on the switches 115 and 116. A line 120 leads from the switch 115 through the juncture 121 and thence to line 122 for the ignition system 123.

In FIG. 9 the Outriggers and the drive axle are shown in the position occupied for normal forward drive of the vehicle. Assuming that the operator has moved the vehicle into a position for stacking a load, the right-hand outrigger lever 56 may be moved to the dotted line position shown which will result in the swinging of the outrigger 29 to an extended position. The current for the ignition system is conducted through line 104, thence through line 105 through switch 106, line 107 to junction 108', thence through line 117 through junction 118,. thence through line 119, switch 115, line 120, junction 121 and line 122 to the ignition system 123. This means that the engine continues to operate and provide hydraulic power for the tilt and hoist cylinders and for the traction at the drive axle. With the outrigger 29 extended and the lever 56 moved to the neutral position shown in full lines, the button 111 is again depressed, maintaining a circuit through the switch 110.

It will be noted that when the lever 56 was moved out of its neutral position to the retract outrigger position, the button 111 was released and the circuit was broken through the switch 110. Now the drive axle motors may be operated so as to turn the drive wheels in opposite directions and thus swing the drive axle assembly 25 about the pivot 9 in a clockwise direction as viewed in FIG. 9.

The movement of the drive axle and the member 31 carried thereby with respect to the pivot 9' releases the button 112 and causes the switch 186 to move to open position. The power circuit to the engine ignition system, however, is now maintained through line 104, through line 185a, thence through the switch 118 to line 109 to the junction 168 and thence to the ignition system 123 as above described.

It will be understood that manipulation of the left-hand outrigger 27 will open the switch at 115- and that the circuit to the engine would be completed through the switch 116, providing the outrigger '29 is in storage position. It will be observed, however, that in the event the operator should attempt to swing the outrigger 27 to extended position when the outrigger 29 is extended, both switches 1,15 and 116 would be open and the circuit to the ignition system 123 would be broken. Accordingly the engine would stop and there would be no source of hydraulic fluid power and the truck could not be manipulated into an unsafe or unstable position. This is a safety feature that would prevent the extension of both Outriggers at the same time.

The electrical interlocking system provided also prevents the retraction of an outrigger with the drive axle turned so as to position the drive wheels along the central axis of the vehicle. Assuming that the outrigger 29 is extended, as above described, and the drive axle assembly is turned 90 from the position shown in FIG. 9 so as to permit operation of the lift truck for stacking, the normal manipulation would call for rotating the drive axle so as to be transverse of the vehicle before the outrigger 29 is retracted. As above pointed out, the circuit to the ignition system, when the drive axle is turned 90 from the position shown, is through the switch 110. The switch 106 has been opened by the turning movement of the cam 113 relative to the switch 106. Now, if the operator should inadvertently attempt to retract outrigger 29 by moving the lever 56, he would open the switch 11!) and thus stop the engine and interrupt the hydraulic fluid power supply.

The importance of this safety feature will be appreciated when it is recognized that when the drive axle is turned from a position transversely of the vehicle to a position with the drive wheels aligned with the central axis of the vehicle, the "load on the forks is eccentric of the vehicle and should be supported by the extended outrigger. The safety provision of the electrical interlock between the drive axle and the Outriggers insures that the load on the lifting forks will always be supported and stabilized by an extended outrigger.

The hydraulic system for the vehicle as illustrated in FIG. includes the power unit 150. It will be understood that the hydraulic system of the instant invention is suited for drive by an electric motor and that when thus driven the electrical resistance units usually employed to vary the speed of drive of the different components in an electrical truck may be eliminaed.

Two hydraulic pumps, preferably of the gear type,

are driven by the power unit 150. The large pump is indicated at 151 and the small pump at 152. Preferably the gear pump 151 has a capacity of about twice the gear pump 152. A reservoir 153 for hydraulic fluid is connected by 'line 154 to the input side of the large pump 151 and by line 155 to the input side of the small pump 152. The output of the large pump is directed through line 156 to port 157 of the tilt-hoist valve 158.

The tilt-hoist valve is preferably of the construction disclosed in my co-pending application Serial No. 849,- 588 which was filed October 29, 1959 (Docket No. 5908). The tilt-hoist valve includes one manually movable plunger 159 which directs hydraulic fluid by way of line 160 to the hoist cylinder 23.

As will be understood by reference to FIG. 1 of the drawings, the cylinder 23 raises and lowers the load along the mast 22 of the lift truck. A second manually operable plunger for the tilt-hoist valve 158 is indicated at 161 and movement of this plunger is effective to direct hydraulic fluid through line 162 to the tilt cylinder 163 or, alternatively, to line 164 to the other end of the tilt cylinder 16-3. It will be understood that the tilt cylinder 163 is a double-acting cylinder and is connected to the tiltable mast 22 of the lift truck so as to tilt the mast with the load carriage thereon.

A line 165 leads from port 166 on the tilt-hoist valve body to a port 167 on the vehicle drive control valve 168. The vehicle drive control valve 168 is preferably of the type disclosed in detail in my said co-pending application Serial No. 849,588, filed October 29, 1959 (Docket No. 5908). In FIG. 10 two views of the vehicle control valve 168 are shown. The lower view of the valve 168 illustrates side 1 of the valve showing the conduit connections between side 1 of the vehicle control valve 168 and the multi-phase valve 170. The uppermost view of the vehicle control valve 168 illustrates side 2 of the valve body and shows a conduit leading to the drive motors and a conduit leading to the multiphase valve 170. The two views of the vehicle drive control valve 168 are enclosed within a phantom outline 168a.

For purposes of clearly illustrating the control units for the hydraulic system, the multi-phase valve 170 is also illustrated so as to show two sides of the valve 170. Side 2 of the multi-phase valve 170 is at the right hand of the phantom line enclosure 170a. This side 2 shows the conduit connections to the vehicle drive control valve 168 and the left-hand showing of the multi-phase valve 170 illustrates the connections between the multiphase valve and the drive motors. The left-hand drive motor is illustrated at 171 and the right hand drive motor at 172.

As will be understood from the instant description and from the disclosure of my co-pending application Serial No. 698,663, filed November 25, 1957 (Docket No. 10458), for normal forward or reverse movement of the vehicle the two drive motors 171 and 172 operate in the same phase so as to drive the vehicle either forward or in reverse. When the vehicle is operated for stacking, as described in connection with FIGS. 6, 7 and 8, the drive motors 171 and 172 are in opposite phase and during opposite phase operation one drive wheel 15 is rotated in one direction and the other drive wheel 16 is rotated in an opposite direction. According to the instant invention the two drive motors 171 and 172 may be operated and guided so as to vary the rotation of the drive wheels relative to each other and thus establish a control for the drive wheels which will guide the vehicle accurately through a range of motion which could not be achieved inthe absence of the multi-phase valve control. With the multiphase valve both motors 171 and 172 may be turned in the same direction but at different rates. In the instant invention the conduits for the hydraulic system and the structure of the valves therefor is such that it is possible to put the motors in displacement without regard to the torque demand on the drive wheels.

The movement of the control plunger 173 of the vehicle drive control valve 168 is preferably determined by manual movement of a foot pedal conveniently accessible to the operator as in my said co-pending application Serial No. 849,588. The manual control of the multi-phase valve 170 is preferably effected by moving the plunger 174 through linkage connected to the hand lever 175 on the steering post which lever is convenient for the operator of the vehicle. It is understood that notches or latches common to the art may be arranged on the steering post so as to hold the hand lever 175 in either of the three distinct phases of operation of the multi-phase valve 170. It will also be understood that the hand lever 175 and the plunger 174 are suited for manual controlling movements between each of the three distinct positions of the multiphase valve.

The output from the small pump 152 is directed by way of conduit 176 to port 177 on the outrigger control valve 178. The outrigger control valve 178 is operated by means of the levers 55 and 56 convenient to the left hand of the operator. The plungers 55a and 56a are movable so as to individually control the movements of the outrigger cylinders 47 and 51. The structure of the outrigger control valve 178 is preferably of the type such as disclosed in my said co-pending application Serial No. 849,588.

'It will be observed that the output from the small pump 152 is conducted in the first instance to the outrigger control valve 178 and thus the carry-over from that output is thereafter directed from the valve 178 by way of line 215 to the drive control valve 168, unless diverted to the outrigger cylinders 57 and 51 by operation of either plunger 55a or 56a. The output from the large pump 151 is connected in the first instance to the tilt-hoist valve 158 and unless diverted to the hoist cylinder 23 or the tilt cylinder 163, the volume from pump 151 is also directed to the vehicle drive control valve 168. This arrangement provides that the outrigger cylinders 51 and 47 may be operated coincident with the lifting of a load on the hoist cylinder 23.

The drive motors 171 and 172 are variable displacement motors such as the motors disclosed in my said copending applications Serial No. 698,663 and Serial No. 849,588. The displacement of the drive motors is controlled by tilting a wobble plate (not shown in the instant application) and such tilting is effected by pressureresponsive means, such as a piston and cylinder (not shown). The control fluid pressure is directed through line 179 leading to the motor 172 and line 180 leading to the motor 171. Said two lines are connected to a line 181 which terminates at port 182 in the vehicle drive control valve 168.

it will be understood that by varying the pressure in the line 181, the displacement position of the wobble plate, and hence the displacement of the motors 171 and 172, is varied. Leakage within the housing of the pump 172 is drained through line 183 and thence by line 184 to the reservoir 153. Similarly a drain line 185 conducts the leakage from motor 171 to the line 184 and thence to the reservoir 153. Fluid is also returned to the reservoir 153 by way of line 186 connected to port 187 on the tilt-hoist valve. A return fluid line 220 leads from the outrigger control valve 178 to the reservoir 153.

As will be understood from said copending applications, the direction of drive on the driving motors 171 and 172 is determined by the direction of fluid flow through the lines connecting the motors 171 and 172 to the multiphase valve 170. A line 188 is connected to the center boss 189 on the motor 172 and the line 188 terminates at port 190 on the multi-phase valve 178. A second fluid pressure line 191 is connected at side port 192 on the motor 172 and the line 191 terminates at port 193 of the multi-phase valve 170. When the drive control valve 168 is moved to a position so as to direct the flow of fluid through line 188 in the direction of the arrow 194, the spent hydraulic fluid coming from the motor 172 by way of line 191 moves in the direction of the arrow 195 back to the multi-phase valve 170. From the multiphase valve the spent fluid is returned through line 210 to the drive control valve, thence through line 222, filter 223 and line 224 to the reservoir. When, however, the drive control valve is moved to a reverse position, hydraulic fluid under pressure moves from the multi phase valve through line 191 in the direction of arrow 196. Such hydraulic fluid after driving the motor 172 returns the spent fluid to the multi-phase valve 178 through line 188 in the direction of the arrow 197.

A similar hydraulic connection is established between the drive control valve 168, the multi-phase valve 170 and the drive motor 171. Line 198 is connected to the motor 171 at port 199 and said line 198 terminates at port 280 in the multi-phase valve 170. The other hydraulic line for motor 171 is the line 201 which is connected to the motor 171 at center boss 202 and terminates in the multi-phase valve at port 203.

It will be understood that when hydraulic fluid is directed from the multi-phase valve to the motor 172 in the direction of arrow 194, hydraulic fluid is also directed by way of line 201 to the motor 171 in the direction of arrow 284. Under such circumstances both motors 171 and 172 are in the same phase and are turning in the same direction. During such phase the hydraulic fluid from the motor is returning to the multi-phase valve in the direction of the arrow 285 along line 198. Both motors may be driven in an opposite direction and in the same phase by reversing the direction of the fluid flow to the multi-phase valve 170 as determined by the vehicle drive control valve 168. Thus the operator directs the vehicle in a forward or reverse direction by the footpedal position reflected in the plunger 173 of the vehicle drive control valve.

A pair of conduits connect the drive control valve 168 to the multi-phase valve 170. One line 207 is connected to port 288 on the drive control valve 168 and terminates at port 209 of the multi-phase valve 170. The other line 210 is connected to the valve 168 at port 211. The line 210 terminates in the multi-phase valve at port 212.

Assuming the plunger 173 is moved to a forward drive position by the foot pedal of the operator. Fluid flow from the pumps to the valve 168 is then directed in the direction of the arrow 213 into the multi-phase valve 170 and such fluid, after being utilized to drive the motors 171 and 172, returns to the drive control valve 168 along line 210 in the direction of the arrow 214. Reversing the position of the plunger 173 will reverse the fluid flow in the lines 287 and 210 so that the motors 171 and 172 are operated in the same phase to drive the vehicle in reverse.

The line 215 is connected to the outrigger control valve at port 220 and the line 215 terminates in the drive control valve 168 at port 217. The output from the small pump 152 when not required to move the Outriggers is carried over by way of line 215 to the vehicle drive control valve. Accordingly, in the event there is no movement of the hoist cylinder 23 or the tilt cylinder 163 or the outrigger cylinders 47 and 51, the output of both motors is directed into the valve body 168. When the vehicle is operated at high speed, the output of both pumps 151 and 152 is available for driving the motors 171 and 172.

A conduit 225 leads from port 225a of the outrigger control valve through pilot operated check valve 226 and thence through line 227 to one end of the double-acting hydraulic cylinder 51. The cylinder 51 is arranged as 1 1 above described to move the right-hand outrigger to and from retracted position. Movement of the outrigger control valve plunger 56a directs fluid under pressure to the right-hand end of cylinder 51 and the piston within the cylinder is thereupon moved so as to extend the piston rod 228 from the cylinder 51.

The fluid within the cylinder at the left side of the piston is moved out of the cylinder by way of line 229, thence through check valve 226 and line 2311 which tenninates at port 231 of the outrigger control valve. The pilot operated check valve 226 is constructed and arranged so as to hydraulically lock the piston rod 228 in either its retracted or extended position. A similar pilot operated hydraulic check valve 232 is arranged in the hydraulic lines leading to the left-hand outrigger cylinder 47.

In FIG. I have illustrated the check valve 226 and it will be understood that the check valve 232 is constructed and arranged like the check valve 226. Re ferring to FIG. 15, the line 225 leads into a bore 233 in the body of the check valve 226. When fluid is directed into line 225, thence through the bore 233 in the direction of the arrow 234, the ball check 235 is raised from its seat by the fluid pressure and the fluid exits from the valve body by way of line 227. The valve body 226 is provided with a transverse bore 236 which terminates in a pilot cylinder 237 and the fluid pressure thus transmitted acts against the piston 238 to raise the check valve 239 from its seat and permit flow through passageway 2411 in the direction of the arrow 241. A similar arrangement is provided by way of transverse passage 242 and piston 243 so as to open the check valve 235 in the event fluid is introduced in the direction of the arrow 244 for a retracting movement of the outrigger.

It will be understood that in the event the outrigger is being retracted, fluid within the cylinder 51 returns to the outrigger control valve 178 in the direction of the arrow 245. It will be understood that in the absence of movement of hydraulic fluid in either direction, the ball check valves 235 and 239 hold the Outriggers in locked position. This provides a hydraulic lock for the outriggeis and insures against the Outriggers drifting away from retracted or extended position in the absence of manual manipulation of the plungers 56a and a.

A line 246 leads from the outrigger control valve 178 through the pilot operated check valve 232, thence through line 247 to one end of the left-hand outrigger cylinder 47. A second fluid line 248 leads from the outrigger control valve 178 through check valve 232, thence through line 249 to the other end of the outrigger cylinder. The detailed description of pilot operated check valve 226 is applicable to the check valve 232.

The multi-phase valve 171} is illustrated in detail in FIGS. 11, 12 and 13. In FIG. 11 the multi-phase valve is in a neutral or normal position for conventional forward drive of the vehicle. The left-hand motor 171 and the right-hand motor 172 are being driven in the same direction for normal drive of the vehicle with the outriggers retracted. During such normal drive the vehicle is steered by the steering wheel 57. Conduit 2117 conducting hydraulic fluid under pressure from the drive control valve leads such fluid into the annular chamber 250. Such fluid under pressure moves out of the space 250 in the multi-phase valve 170 through port 251, conduit 201 and through the motor 171. The spent fluid returns from the motor 171 through line 193 and port 252 into the space 253 within the valve body. The fluid under pressure for driving the motor 172 moves from space 251} through the port 254, thence into space 255, out port 256 through line 138 to the moto 172. The spent fluid from the motor 172 leaves the motor by way of line 191 and discharges by way of port 257 into space 253. The spent fluid from both motors, that is, the fluid in space 253 and the fluid in space 258, is moved into space 259. A port 260 in the space 259 discharges into a conduit 210 lead- 12 ing from the multi-phase valve to the vehicle drive control valve 168.

When it is desired to rotate the drive axle by placing the motors in opposite directional rotation, the multiphase valve 170 is moved to the position illustrated in FIG, 12. This is accomplished by moving the valve plunger 174 inwardly as indicated at position B of FIG. 12. Hydraulic fluid under pressure enters the multiphase valve 170 through the conduit 207 and fills the space 250. Such fluid is directed out of the space 250 by way of port 251, line 201 to the motor 171 which is driven in the same directional rotation as illustrated in FIG. 11. The spent fluid leaves the motor by way of line 198 and thence into space 253 by way of port 252.

The plunger 174 is provided with an elongated land which terminates in a shoulder at 262. A space is provided at 263 between the end of the shoulder and the edge of the port 264 whereby fluid from the space 253 is directed to flow into space 258. The narrow land 266 on the plunger has closed the port 267 so that the hydraulic fluid from the space 253 may not escape into chamber 25 Accordingly, hydraulic fluid in the space 258 is discharged through the port 257 into conduit 191 to motor 172 so as to drive the motor 172 in a direction opposite the direction of drive illustrated in FIG. 11. The fluid from motor 172 is conducted by way of line 188 into space 255 by way of the port 256. The movement of the plunger 174 from the position A of FIG. 11 to the position of FIG. 12 uncovers a transverse bore 268 in the land 269. Thus fluid in the space 255 may escape from the space 255 through the transverse bore 268 into the longitudinal chamber 27 0 formed centrally of the plunger 174. The fluid received within the chamber 270 then exits through another transverse bore 271 formed in the land 272. Thus the fluid from the motors is discharged from the transverse bore 271 into the space 259 and exits through the passageway 273 into conduit 210 leading from the multi-phase valve 170 to the drive control valve 168.

The transverse bore 271 which terminates in the land 272 is provided with a milled groove 275. The groove 275 in the land 272 provides a metering groove to obtain accurate control of the hydraulic fluid permitted to bypass one or the other motor.

When the lift truck is arranged as illustrated in FIG. 7 with the outrigger 29 extended and the drive axle turned at right angles to the vehicle with respect to the stack indicated at S, it is important that both drive wheels turn at the same speed and in the same direction so that the forks 19 and 211 will go straight into the stack indicated at S. During such operation the drive motors should not be aifected by differences in load which might be caused by bumps in the floor. The term guidance as used herein is for guiding the drive wheels and fork assembly into the stack in the event the operator does not have the truck stopped in the aisle with the drive wheels accurately lined up with the stack. The operator, by manipulating the lever 175 on the steering column, may move the plunger 174 of the valve 170 within certain limits here described and thus eflect variations in rotation of one drive wheel relative to the other and thus, in effect, hydraulically steer the drive wheels and the forks 19 and 2t) accurately into the stack. Once the operator has, by moving the plunger 174, guided the drive wheels and the forks 19 and 20 accurately into alignment with the stack, the plunger is restored to the position indicated at C in FIG. 13 and the drive wheels then turn in unison in the same direction to continue the motion of the forks into the stacking position. With the plunger 174 in the position indicated at C in FIG. 13, the spaces formed by the cavities in the valve body 170 and the lands on the plunger 174 are arranged so that the motors are in full series circuit with all of the fluid going through each motor and thus the drive wheels must turn at the same speed and they are not aifected by the loads which may be imposed on the drive wheels individually by bumps in the floor.

The inward guidance range of the drive wheels is indicated by the space C to C in FIG. 13 and the outward guidance range is indicated by the space between C and C in FIG. 13.

As will be understood, the path of fluid flow through the multi-phase valve 170, as shown in FIG. 13, is first by way of line 207 into the space 250, thence through port 251 and line 201 to the hydraulic motor 171. The fluid flow from the motor 171 is by way of line 198, thence into space 253 by way of the port 252 into space 279, thence axially of the valve body into space 255 to the port 256 which leads to the motor 172 by way of line 188. Fluid from the motor 1'72 thence travels by way of line 191 to port 257 which terminates in space 258. From space 258 the fluid moves axially into space 259 and thence from the displacement valve body 170 by way of port 260, passage 273 and line 210 leading to the drive control valve 168.

With the plunger 174 of the valve 170 arranged in full line position as indicated by position C in FIG. 13, and thereafter moved further to the left toward the position indicated at position C the transverse bore 268 in the land 269 opens into the space 250 by reason of the counterbore forming the shoulder at 278. Coincident with this movement of the plunger 174 toward position C the milled groove 275 opens into space 253 by reason of the shoulder 279a. Under this circumstance a limited amount of hydraulic fluid may move from space 250 into the transverse bore 268 and thence through the central bore 270 and through milled groove 275 into space 253.

The limited amount of fluid which is permitted to move through this path thus by-passes the left-hand motor 171 but is directed into the right-hand motor 172. The fluid thus metered into space 253 moves into space 255 and thence into the right-hand motor 172 by way of conduit 188. The fluid from the right-hand motor 172 moves through conduit 191 and port 257 into space 258. Such fluid from space 258 is conducted out of the multi-phase valve 170 by way of passageway 273 and space 259. The discharge from 273 is conducted by way of conduit 210 to the drive control valve 168. The left-hand motor 171 accordingly rotates slower than the right-hand motor 172 since a part of the fluid normally directed to the left-hand motor is by-passed to the righthand motor. In this way accurate guidance toward the left of the two drive wheels is accomplished while moving the forks and front drive axle into stacking position.

It will be understood by the preceding description that a reversing of the plunger 173 in the drive control valve 168 will reverse the direction of flow through the multiphase valve so that guidance is provided for the drive wheels when the vehicle is reversed as, for example, in moving a load out of a stack.

Referring again to FIG. 13, and assuming that the plunger is pulled outwardly from the position C as indicated in full lines to a position indicated at C The result of the plunger movement toward position C opens the transverse bore 268 to the space 255 by reason of the undercut indicated at 280. The second transverse bore, namely, 271, opens into space 259 by reason of the undercut 281. The amount of hydraulic fluid which moves from space 255 through the transverse bore 268 into the longitudinal bore 270 and thence through transverse bore 271 and metering groove 275 is by-passed into the discharge passageway 273 rather than being directed to the right-hand motor 172. Accordingly, the right-hand motor 172 rotates slower than the left-hand motor 171 by the amount of the fluid which is by-passed. Accordingly, the front end of the vehicle is then guided toward the right as it is being driven forward. As in the situation previously described for guiding the vehicle to the left, the vehicle control valve may be reversed and 14 thus when the vehicle is backed away from the stack, the guiding is to the left. The rate of guiding, that is, the difference between the revolutions per minute of the two drive wheels, even though in the same phase, is thus accurately controlled by the operator with the lever 175 mounted on the steering column.

As will be understood from reference to my said co pending application Serial No. 849,588, filed October 29, 1959, (Docket No. 5908), the vehicle control valve includes a displacement valve which operates to control the displacement of the drive motors in accordance with the torque demand at the drive wheels of the vehicle. The lift truck of the instant application also includes a displacement control valve 300 which is mounted on, or forms a part of the drive control valve 168. For clarity and explanation, the displacement control valve 300 in the instant case is disclosed within the phantom outline 168a.

The displacement control valve 300, during the conventional drive of the lift truck, operates in response to the torque demand at the drive wheels to place the hydraulic drive motors in position of displacement corresponding to the torque requirement substantially as described in detail in my co-pending application Serial No. 849,588 (Docket No. 5908). In the displacement valve 300 of the instant application, however, a line from the displacement valve leads to the multi-phase valve so that when the multi-phase valve is operated in either of the phases shown in FIGS. 12 or 13, the displacement valve 300 will be operated to place the motors in maximum displacement position.

Referring to FIG. 14, the valve body, indicated in its entirety as at 300, is provided with an inlet 167a which comes from a high pressure area in the drive control valve. It will be noted from the hydraulic diagram of FIG. 10 that the output of the large pump 151 leads through the tilt-hoist valve 158 and thence to a port 167 in the vehicle control valve 168. The high pressure line 167a leads from this high pressure area in the control valve 168 to the transverse passageway 303 in the displacement valve 300. A chamber 307 is provided within the valve body 300 which is in communication with the inlet 303. A bore, located beneath the chamber 387, receives the spring pressed plunger 304. Located at the right side of the valve body is a conduit 181 which leads by way of branches 179 and 188 to the drive motor control. It will be understood that when high fluid pressure leaves the displacement valve by line 181, it moves the wobble plate in the drive motors to the position of maximum displacement. Lower pressures in line 181 reduce the displacement. At the top of the displacement valve 300 is a line 167b which connects a space 167a within the displacement valve to a relief flow sensing means within the drive control valve 168.

Reference is made to my said co-pending application, Serial No. 849,588, which illustrates and describes in detail the drive control valve which is provided with a relief flow sensing means. The relief flow means of the drive control valve 168 in the instant case is similarly constructed and includes a restricted flow passage between the high pressure and low pressure areas within the drive control valve 168. The said copending application, Serial No. 849,588, also includes a detailed description and showing of a displacement valve and the operative relationships between the displacement valve and the relief flow sensing means in the drive control valve 168. A generally similar displacement control valve 300 is provided in the instant system and includes modifications for fluid conduit connections to the multi-phase valve 170 of the instant application.

Referring to FIGS. 10 and 14 of the drawings, fluid conduit lines 167a, 301, 167i) and 181 are shown as esestablishing the hydraulic connections between the multiphase valve 170, the drive motors 171 and 172 and the relief flow sensing means forming a part of the drive control valve 168. It will be understood that under certain conditions of operation of the vehicle such as, for example, a quick reversal of the position of the plunger 173 of the drive control valve 168 when the lift truck is going at full speed, would result in the drive motors 171 and 172 functioning as pumps since they would be driven as pumps by the momentum of the vehicle. When thus driven as pumps due to the reversal of the plunger 173, they would (in the absence of protective means) demand a fluid supply approximately three times the maximum volume (maximum total pump output) as when they are performing normally as motors. Due to the lack of such fluid supply, the motors acting as pumps would cavitate and might be damaged.

In the device of FIG. 14 of the instant application the plunger 314 arranged in the bore at the right-hand side of FIG. 14 performs the function of a relief flow sensing valve which responds to the relief flow sensing means in valve 168 and protects the motors under the conditions described above. The fluid pressure coming into the valve body 31111 by way of line 1671) would be relatively high under relief flow conditions and such higher pressure would be eflective to move the plunger 314 downwardly as viewed in FIG. 14.

As will be understood from the preceding description, the line 181 leading to the displacement control for the motors places the motors in different positions of displacement in response to different fluid pressures transmitted to the motors by way of line 181.

Under conditions of normal forward drive of the lift truck, that is, with the drive axle transversely of the vehicle, the line 301 coming from the displacement valve body 300 serves as a drain line and thus the chambers 312 and 313 at the lower portion of the valve body 300 (as viewed in FIG. 14) may be drained by way of passage through the multi-phase valve. Under other conditions of vehicle operation, that is, with the multiphase valve moved to the position shown in FIGS. 12 and 13, high fluid pressure is brought into the chambers 312 and 313 in the valve body 301) by way of the line 3111. Accordingly, the dual functions of the line 301 are determined by the phase position of the multi-phase valve 17 0'.

The displacement valve plunger, indicated in its entirety as at 3114, is provided with a land 385 having a close sliding fit in the bore which receives the plunger. A land 3115a above the land 3% is provided with a lesser diameter and is also provided with vertical grooves, or the like, so that high fluid pressure entering the body by way of line 167a is eifective over the upper side of the land 3115. Beneath the land 3135 is an annular chamber 3&6 formed on the plunger 3114 and a vertical groove 311 is formed on the plunger beneath the annular space 306. The groove 311 thus opens the space 3116 to chamber 312 which extends upwardly around the cup 31 engaging the plunger 3%. With the parts in the position as shown in FIG. 14, the annular space 3% on the plunger 3114 is also opened into the transverse bore 316 and the righthand end of the bore 316 in turn opens into an annular space 315 on the flow sensing valve plunger 314. Accordingly, the line 181, which leads to the displacement control in the motors 171 and 172, is opened through the path described so as to lower the pressure in line 181 and drain such fluid pressure as may exist from line 181 outwardly through the line 3111 leading to the displacement valve 171 It will be observed that increasing fluid pressure by way of the line 167 a will be effective over the upper surface of the land 3115 and will be effective to overcome the spring 3118 around the cup 309 which spring normally biases the plunger 3*.34 to its upper position as shown in full lines in FIG. 14. As the plunger 3% moves downwardly in response to such higher fluid pressure, the land 3115 will be positioned so that its upper surface opens into the transverse passage 316 and the higher fluid pressure is then moved into the annular chamber 15 on the sensing valve plunger 314 and thence into the line 181 and thence to the motors tending to move the displacement control in the motor to a position of greater displacement.

In the event the sensing valve plunger 314 is moved downwardly against the bias of its spring 317, the annular chamber 315 will then open into the lower transverse bore 316a and thus line 181 may drain by way of the annular chamber 315, thence into transverse bore 316:: and outwardly by way of line 3111. In this way a second flow path is established within the valve body 301 between line 301 and line 181.

In the event the multi-phase valve is moved to the positions of FIGS. 12 and 13, the check valve system within the multi-phase valve is effective to introduce high fluid pressure into the displacement valve 300 by way of line 301. In that event the flow sensing valve plunger 314 is moved upwardly to the position shown in full lines in FIG. 14 and the plunger 304 is also moved upwardly so that the upper end thereof abuts the bottom of the plug 310. High fluid pressure then moves upwardly along the groove 311 formed at the lower end of the plunger 304 and into the annular space 306 and thence laterally through passageway 316 into the annular chamber 315 on the plunger 314 and outwardly of the valve body 300 into the line 181. Thus the drive motors 171 and 172 are placed in the position of maximum displacement by reason of the high fluid pressure introduced into the displacement valve body 3110 from the multi-phase valve 171 by Way of line 3111.

With the multi-phase valve in the position shown in FIG. 11, that is, the position for conventional drive of the vehicle, the low pressure drainage fluid from the dis placement control valve enters the multi-phase valve by Way of conduits 3111, thence through passageway 350 and bore 351 into an annular space 352 on the cup 353 integrally formed with the plunger 174. Openings 354 lead from the annular space 352 into the space 355. Fluid escapes from the multi-phase valve 170 by way of passage 356 connected to conduit 221 which leads to the low pressure space in the drive control valve 168. According, it will be understood that for conventional drive of the vehicle, the multi-phase valve 170 does not affect the action of the displacement control valve 300 and the displacement control valve 300 thus functions in a manner described in detail in connection with my said co-pending application, Serial No. 849,588.

When, however, the multi-phase valve is moved to the position illustrated in FIG. 12, it will be observed that the member 353 has been moved so that a land 357 thereon prevents the fluid coming from the displacement valve by Way of line 3G1 from moving out of the multiphase valve by way of line 221.

The reduced diameter portion 358 on the member 353 places the passageway 351 in communication with a parallel passage 359. A bore 361) provided with check valve 361 connects the space 250 in the multi-phase valve 170 in communication with the passageway 359.

in the foregoing description of the displacement valve 3%, reference has been made to a mode of operation of the displacement valve 360 wherein hydraulic fluid under pressure is moved from the multi-phase valve 170 into the lower end of the displacement valve 309 and such fluid pressure in turn moves the drive motors to maximum displacement position. The multi-phase valve structure, illustrated in FIGS. 11, 12 and 13, includes a check valve system which is eflective to divert high fluid pressure into line 3111 leading from the multi-phase valve 170 to the displacement valve 300.

With the plunger in the position illustrated in FIG. 11, which is the position for normal forward drive of the vehicle, line 3111 leads by way of inlet 35%) and passageway 351, thence through openings 354 formed in the annular chamber 352 of the plunger 374 into the chamber 355 at the left-hand end of the valve body and outwardly of the valve body by way of line 221. The check valve system includes a passageway 359 opening into an annular chamber 358 formed on the outer surface of the left-hand end of the plunger 174. In the position of the plunger 174 shown in FIG. 11 there is no outlet for the chamber 358 and no fluid may move from the interior of the multi-phase valve into line 301. When the plunger 174 is in either the FIG. 12 or FIG. 13 position, the line 359 is open to the line 301 and the check valve system is effective to transmit fluid pressure to valve 300.

The check valve system includes a branch 360 opening into the space 250 and a second branch 359a having ball check 35% leading by way of passage 365 into space 259 at the interior of the multi-phase valve 170. When fluid is moving into the multi-phase valve at high pressure by way of line 207, the space 250 is filled with high pressure fluid and a portion of such fluid may move from the chamber 250 by unseating the ball check 361 and thence by way of line 359 into the annular space 358 and thence outwardly of the multi-phase valve by way of line 301. During this condition of operation the ball check 35% prevents high fluid pressure in the check valve system from moving into space 259. This mode of operation is illustrated in FIGS. 12 and 13.

In the event the manually operated plunger 173 in the drive control valve 168 is reversed so that high fluid pressure enters the multi-phase valve by way of line 210, the space 259 is filled with fluid at high pressure. Such high fluid pressure may be conducted by way of line 365 to unseat the ball check 35911 and thence by way of line 359 into the annular space 358 and outwardly of the multiphase valve by way of line 301. During this mode of operation (FIGS. 12 and 13) the high fluid pressure in line 359 and 359a maintains the ball check 361 closed and prevents high fluid pressure from entering the space 250.

Hydraulic fluid returned from the motors after driving the traction motors 171 and 172 is directed through the conduits above described to the drive control valve 168. The spent or low pressure hydraulic fluid is moved from the drive control valve by way of line 222', thence through a filter 223 and line 224 to the reservoir 153. Line 221a conducts fluid from port 221b of the multi-phase valve to the reservoir 153. The arrangement illustrated employing two pumps of different capacities and directing the output of one pump 152 in the first instance to the outrigger control valve and the output of the other pump 151 to the tilt-hoist valve results in an efficient utilization of the power unit. The energy derived from the power unit may be utilized to extend or retract the Outriggers and to raise and tilt the load on the mast, which operations do not ordinarily take place when the vehicle is moving. Assuming the load is elevated and tilted on the mast and the outriggers have been retracted, then the energy of the power unit is available for driving the vehicle. At high speed operation of the vehicle the output of both pumps 151 and 152 may be utilized for traction effective to move the load.

It is believed that the mode of operation and the advantages obtained from the lift truck made according to the instant disclosure will be apparent to those skilled in the art. Generally speaking, the adoption of the vehicle for a warehouse results in allowing more than 35% more material to be stored in a given fioor area than with the prior art vehicles. For conventional driving of the lift truck, the outriggers are retracted. The operator steers the vehicle by means of the wheel 57 in a conventional manner, the internal combustion engine 150 is accelerated in the usual manner by a foot throttle and the position of the drive control valve 168 is determined by the foot pedal engaged by the operator.

When it is desired to swing one of the outriggers, for example, the outrigger 27, for left-hand stacking, the lefthand lever 55 is moved by the operator. The extension of the outrigger raises the left-hand steering wheel from the floor as illustrated in FIG. 6 and the displacement control valve is manually operated to rotate the front axle as illustrated in FIGS. 8 and 12.

As described above, the drive wheels may be operated at different rates in the same direction for guiding the vehicle accurately into stacking position.

When the left-hand outrigger is extended for maneuvering the vehicle into a stack, the linkage illustrated in FIG. 2 is effective to'control the position of the dirigible Wheels 16 and 17. Accordingly, when the vehicle is maneuvered to the position of FIG. 8, the dirigible wheel 17 is brought into alignment with the outrigger 35. Thus, in effect, the width or tread of the vehicle has been increased to provide a width corresponding to the distance between the wheel 17 and the wheel 35. This results in great stability immediately adjacent the load which is being handled on the forks.

Coincident with the hydraulic manipulation of the outrigger and the drive axle, and the controls therefor, is the electrical interlock illustrated in FIG. 9. As described in detail above in connection with the electrical interlock, it is impossible for unskilled or inexperienced operators to maneuver the vehicle into an unstable position. The electrical interlock provides a safety feature which stops the engine and thus the source of hydraulic power in the event it is attempted to extend both outriggers at the same time or turn the drive axle before an outrigger has been moved so as to permit the drive wheel to be moved to the position shown in FIGS. 7 or 8.

Coincident with the manipulation of the Outriggers, the pilot operated check valves in the outrigger hydraulic circuit provides an hydraulic lock to hold the Outriggers in their extended or retracted position.

Although I have illustrated and described one form of my invention in considerable detail, it will be appreciated by those skilled in the art that numerous variations may be made therein without departing from the scope of the invention as defined in the following claims.

What is claimed is:

1. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit, dirigible wheels carried beneath said rear frame portion, said frame having a relatively narrow centrally disposed forward portion, a transverse drive axle pivotally mounted at the outer end of said narrow forward portion of the frame to provide a space at each side of the lift truck between the drive axle and the rear portion of the frame, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the free outer end of the outrigger arm, means to swing the outrigger arm and the wheel carried thereby from a storage position in said space at the side of the lift truck to a laterally extended position at the side of the lift truck, means operatively connecting the outrigger arm and the dirigible wheels to align one of the dirigible wheels with an outrigger wheel at the opposite side of the frame when the outrigger is extended, said last-named means including a first link moved by the said one dirigible wheel and a second link moved by the outrigger arm and a lost-motion connection between the first and second links whereby outrigger movement is transmitted to the dirigible wheel but the dirigible wheel may be moved independently of the outrigger.

2. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit, dirigible wheels carried beneath said rear frame portion, said frame having a relatively narrow centrally disposed forward portion, a transverse drive axle pivotally mounted at the outer end of said narrow forward portion of the frame to provide a space at each side of the lift truck between the drive axle and the rear portion of the frame, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the free outer end of the outrigger arm,

means to swing the outrigger arm and the wheel carried thereby from a storage position in said space at the side of the lift truck to a laterally extended position at the side of the lift truck, means on each outrigger engaging means on said drive axle at opposite sides of the drive axle pivot, means operatively connecting the outrigger arm and the dirigible wheels to align one of the dirigible wheels with an outrigger wheel when the outrigger is extended, said last-named means including a first link moved by the said one steering wheel and a second link moved by the outrigger arm and a lost-motion connection between the links whereby outrigger movement is transmitted to the dirigible wheel, a steering wheel to turn the dirigible wheels independently of the outrigger movement, said independent turning of the dirigible wheels being accommodated by said lost-motion connection of said links.

3. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit, hydraulic pump means driven by said power unit, dirigible wheels carried beneath said rear frame portion, a steering wheel on the frame for manual turning of the dirigible wheels, said frame having a relatively narrow centrally disposed forward portion, a transverse drive axle pivotally mounted at the outer end of said narrow forward portion of the frame to provide a space at each side of the lift truck between the drive axle and the rear portoin of the frame, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the free outer end of each outrigger arm, interengaging lugs on the drive axle and the outriggers, means to swing one outrigger arm and the wheel carried thereby from a storage position in said space at the side of the lift truck to a laterally extended position at the side of the lift truck, said movement of the outrigger freeing its lug from the drive axle, means operatively connecting the outrigger arm and the dirigible Wheels to align one of the dirigible wheels with an opposite side outrigger wheel when the outrigger is extended, said last-named means including a pair of links having a lost-motion connection between the links whereby outrigger movement is transmitted to the dirigible wheel but the dirigible wheel may be moved manually by the steering wheel independently of the outrigger, hydraulic drive motor means on the drive axle to turn the same in the direction of an extended outrigger, and valve and conduit means to direct fluid from said pump means to the drive motors and the means for swinging the Outriggers.

4. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit and hydraulic pump, dirigible wheels carried beneath said rear frame portion, rocker means pivoted on the frame connecting the dirigible wheels to each other for joint turning movement, said frame having a relatively centrally disposed forward portion, a manually operable steering wheel connected to said rocker means, a transverse drive axle pivotally mounted on a vertical pivot at the outer end of said forward portion of the frame to provide a space at each side of the lift truck between the drive axle and the rear portion of the frame, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the outrigger arm, hydraulic cylinder means connected to said hydraulic pump to swing one outrigger arm and the wheel carried thereby from a position in said space to a laterally extended position at one side of the lift truck, links connecting the said outrigger and said rocker means, parallel member's fixed to said drive axle extending rearwardly therefrom adjacent the drive wheels into said storage space at each side of the lift truck, a lug carried by each of said outriggers at the extreme outer free end thereof, said lugs being aligned to engage with the outer free end of said parallel members to prevent pivotal movement of the drive axle into said storage space when the outrigger is retracted, said links moving said rocker means to align a dirigible wheel on the other side of the lift truck with the extended outrigger Wheel on said one side of the lift truck.

5. A lift truck comprising a frame having a rear portion supporting a power unit and hydraulic pump means, dirigible wheels carried beneath said rear frame portion, means connecting the dirigible wheels for joint turning motion, a manual steering wheel for said dirigible wheels, said frame having an elongated centrally disposed forward portion, a transverse drive axle pivotally mounted on a vertical pivot at the outer end of said elongated forward portion of the frame to provide drive wheel and outrigger storage space at each side of the lift truck be tween the forward and the rear portion of the frame, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, said Outriggers being disposed in said storage space when retracted, an outrigger wheel mounted on the free outer end of the' outrigger arm, hydraulic cylinder means connected to said pump means to swing the outrigger arm and the wheel carried thereby from a retracted position in said storage space to a laterally extended position at the side of the lift truck, rigid parallel locking members fixed to said drive axle extending rearwardly therefrom adjacent the drive wheels into said storage space at each side of the lift truck, a locking lug carried by each of said outriggers at the extreme outer free end thereof, said lugs being engaged with said locking members to prevent pivotal movement of the drive axle into said storage space on one side when the outrigger is retracted on said one side of the frame, said pivotal mounting of the outrigger on the frame being inclined to raise the outrigger wheel to a higher position relative to the lift truck when retracted and to lower the outrigger wheel relative to the lift truck when extended.

6. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit, dirigible wheels carried beneath said rear frame portion, a steering wheel, means connecting the steering wheel and said dirigible wheels, said frame having a relatively narrow centrally disposed forward portion, a transverse drive axle pivotally mounted at its mid-portion on a vertical pivot at the outer end of said narrow forward portion of the frame to provide drive wheel and outrigger storage space at each side of the lift truck between the forward portion of the frame and the rear portion of the frame, an out-- rigger arm pivotally mounted on an inclined pivot at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the free outer end of the outrigger arm, means to swing the outrigger arm and the wheel carried thereby from a raised position in said storage space to a lower laterally extended position at the side of the lift truck, rigid locking bars carried by said drive axle and extending rearwardly therefrom adjacent the drive wheels into said storage space at each side of the lift truck, a locking lug carried by each of said Outriggers at the extreme outer free end' thereof, said locking lugs being in engagement with the outer free end of said locking bars to prevent movement of the drive axle about its pivot into said storage space: when the outrigger is retracted.

7. A lift truck comprising a frame having a rear por tion, dirigible Wheels carried beneath said rear frame portion, rocker means connecting the dirigible wheels for joint turning movement, said frame having a relatively narrow centrally disposed forward portion, a transverse drive axle pivotally mounted at the outer end of said narrow forward portion of the frame to provide a space at each side of the lift truck between the front and rear portions of the frame, an outrigger arm pivotally mounted at each side of the life truck on the rear portion of the frame, said pivot mounting for the outrigger arm being inclined rearwardly, an outrigger wheel mounted on the free outer end of the outrigger arm, means to swing the outrigger arm and the wheel carried thereby from an elevated storage position in said space at the side of the lift truck to a lower laterally extended position at the side of the lift truck, a manually operable steering wheel for normal guidance of the lift truck by the operator with the Outriggers retracted, said rocker means including a rocker bar pivoted intermediate its ends to the frame, a reciprocating link connected to said rocker bar at each side of its pivot mounting, said reciprocating links being moved longitudinally of the frame in response to joint turning movement of the dirigible wheels, a bell crank mounted on the lift truck frame adjacent each outrigger, a first bell crank link connecting one arm of the bell crank to the outrigger and a second bell crank link connecting the other arm of the bell crank to said reciprocating link, said last-named connection to the reciprocating link providing a lost-motion coupling whereby movement of an outrigger is effective to turn said dirigible wheels but movement of the dirigible wheels by the said manually operable steering wheel is independent of outrigger movement.

8. A lift truck comprising a frame having a relatively wide rear portion, dirigible wheels carried beneath said rear frame portion, said frame having a relatively narrow centrally disposed forward portion, a drive axle mounted at the outer end of said narrow forward portion of the frame to provide a storage space at each side of the lift truck between the drive axle and the rear portion of the frame, said drive axle pivotally mounted for rotation from a first position normal to the longitudinal center line of the lift truck to a second position in alignment with said center line, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the free outer end of the outrigger arm, means to swing the outrigger arm and the wheel carried thereby from an elevated storage position in said space at the side of the lift truck to a lower laterally extended position at the side of the lift truck, a steering wheel for guidance of the lift truck by the operator with the drive axle in said first position and the outriggers retracted, an oscillating bar connected to each of said dirigible wheels, said bar being pivotally mounted on said rear frame portion, a bar link mounted at each end of said bar, each link being moved longitudinally of the vehicle in response to turning movement of the dirigible wheels, a bell crank mounted on the lift truck frame adjacent each outrigger, first means connecting one portion of the bell crank to the outrigger and second means connecting another portion of the bell crank to said bar link, said lastnamed connection providing a lost-motion coupling between the second means and said bar link whereby movement of the outrigger is effective to turn one of said dirigible wheels and movement of a dirigible wheel by the steering wheel is independent of outrigger movement.

9. A lift truck comprising a frame having a rear portion, a power unit and pump driven by the power unit, dirigible wheels carried by said rear frame portion, said frame having a centrally disposed forward portion, a drive axle mounted at the outer end of said forward portion of the frame to provide a space at each side of the lift truck between the drive axle and the rear portion of the frame, said drive axle being pivoted on the frame for movement to a first position transverse of the vehicle and to a second position with the axle aligned longitudinally of the Vehicle, hydraulic motor means on the drive axle to turn the drive wheels, an outrigger arm pivotally mounted at each side of the lift truck on the rear portion of the frame, an outrigger wheel mounted on the free outer end of the outrigger arm, hydraulic cylinder means to swing the outrigger arm and the wheel carried thereby from a storage position in said space at the side of the lift truck to a lower laterally extended position at the side of the lift truck, a steering wheel for guidance of the dirigible wheels by the operator with the Outriggers retracted and the drive axle in said first position, a crank mounted on the lift truck frame adjacent each outrigger, means connecting the crank 22' to the outrigger and to the dirigible wheels, said last-named connection providing a lost-motion coupling between the outrigger and the dirigible wheels effective to turn said dirigible wheels in response to outrigger movement.

10. A lift truck comprising a frame having a relatively wide rear portion, a power unit, hydraulic pump means driven by said power unit, dirigible wheels beneath said relatively wide rear portion of the lift truck, a steering wheel arranged above the frame for manual turning of said dirigible wheels, said frame having a narrow elongated neck projecting forwardly at the longitudinal center thereof, a drive axle pivotally connected at the outer end portion of said forwardly extending neck, an outrigger arm pivotally mounted on the frame adjacent the dirigible wheels, an outrigger wheel carried at the outer end of each outrigger arm, double-acting hydraulic cylinder means interposed between the outrigger arm and the frame to swing the outrigger from an extended position laterally of the lift truck into a retracted storage position along the side of the lift truck, valve and conduit means interposed between said hydraulic pump and said double-acting hydraulic cylinder means for controlling the movements of the outrigger, pilot check valve means in said conduits to provide a hydraulic lock for holding the outrigger in its extended and retracted position.

11. A lift truck comprising a frame having a rear portion supporting a power unit, hydraulic pump means driven by said power unit, dirigible wheels beneath said rear portion of the lift truck, a steering wheel arranged above the frame for manual turning of said dirigible wheels, said frame having a drive axle mounted at the forward end thereof, an outrigger arm pivotally mounted on the frame adjacent the dirigible wheels, an outrigger wheel carried at the outer end of each outrigger arm, a double-acting hydraulic cylinder interposed between the outrigger arm and the frame to swing the outrigger from a lower extended position laterally of the lift truck into a higher storage position along the side of the lift truck, a conduit interposed between said hydraulic pump and opposite ends of said double-acting hydraulic cylinder means for directing fluid into the cylinder and controlling the movements of the outrigger, pilot check valve means in each of said conduits to provide a hydraulic lock for holding the outrigger in either extended or retracted position.

12. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit, hydraulic pump means driven by said power unit, dirigible wheels beneath said relatively wide rear portion of the lift truck, a steering wheel arranged above the frame for turning said dirigible wheels to guide the lift truck for forward drive, said frame having a narrow elongated upwardly arched neck projecting forwardly at the center thereof, a drive axle pivotally connected at the outer end portion of said forwardly extending neck, drive wheels at each end of the drive axle, hydraulic motor means for each drive wheel to turn the drive axle to position one drive wheel under said upwardly arched neck portion, an outrigger arm pivotally mounted on the frame adjacent the dirigible wheels, an outrigger wheel carried at the outer end of each outrigger arm, double-acting hydraulic cylinder means interposed between the outrigger arm and the frame to swing the outrigger from a storage position to an extended position laterally of the lift truck whereby said one drive wheel may be positioned under said arched neck, valve and conduit means interposed between said hydraulic pump and said double-acting hydraulic cylinder means for controlling the movements of the outrigger, pilot check valve means in said conduits to provide a hydraulic lock for holding the outrigger in either said extended or retracted position,

13. A lift truck comprising a frame having a relatively wide rear portion supporting a power unit, hydraulic pump means driven by said power unit, dirigible wheelsbeneath said relatively wide rear portion of the lift truck, a steering wheel for turning said dirigible wheels to guide the lift truck for normal forward drive, said frame having a narrow elongated neck projecting forwardly at the center thereof, a drive axle having drive wheels, said axle being pivotally mounted on a vertical pivot at the outer end portion of said forwardly extending neck to provide a storage space at each side of the vehicle between the drive wheels and the dirigible wheels at the rear of the lift truck, an outrigger arm at each side of the lift truck, said arm having one end thereof pivotally mounted on the frame adjacent the dirigible Wheels, an outrigger wheel carried at the outer end of each outrigger arm, hydraulic cylinder means connected to said pump and having a piston rod connected to the outrigger arm to swing the outrigger from a lowered extended position laterally of the lift truck into an elevated position in said storage space between the drive wheels and the dirigible wheels, said power unit comprising an internal combustion engine having a battery-powered ignition system, said ignition system including an electric circuit means interposed between said battery and said power unit, switch means in said circuit operatively connected to said outriggers, a manually operable hydraulic valve member for each outrigger cylinder means, a valve switch operatively connected to each of said manually operable valve members, a drive axle switch moved by said drive axle in response to axle turning movement about its vertical pivot, said valve switch and said drive axle switch and said outrigger switches connected in said circuit between the battery and the power unit to stop the power unit and pump in response to opening of both outrigger switches at the same time.

14. A lift truck of the type having an outrigger at each side of the truck and having a drive axle pivoted for rotation relative to the lift truck frame, a power unit, a first hydraulic pump and a second hydraulic pump driven by said power unit, said first hydraulic pump having a capacity of about twice the capacity of the second hydraulic pump, a drive wheel at each end of said pivoted drive axle, a variable displacement motor for each drive wheel, said Outriggers being pivoted to the frame of the lift truck, double-acting hydraulic cylinders interposed between the frame and the outrigger to swing the outrigger from a storage position alongside of the lift truck frame to a position extending laterally of the lift truck frame, an outrigger control valve, a mast structure carried by said drive axle, a load platform mounted on said mast structure, hydraulic cylinder means for tilting the mast, hydraulic cylinder means for hoisting said load platform, a tilt-hoist valve for directing fluid to said hoisting and tilting cylinders, a manually operated vehicle drive control valve, a displacement valve responsive to torque demand at the drive wheels to vary the displacement of the drive motors, a manually operable multiphase valve to effect different phases of hydraulic operation of the drive motors, conduit means connecting the output of the first pump to said tilt-hoist valve, conduit means connecting the output of said second pump to said outrigger control valve and conduit means to direct the carry-over of the output from both pumps at the tilthoist and outrigger valves to said vehicle drive control valve, and conduit means to direct hydraulic fluid to said drive motors through said vehicle drive control valve and through said multi-phase valve.

15. A lift truck of the type having an outrigger at each side of the truck and having a drive axle pivoted for rotation relative to the lift truck frame from a position transverse of the truck to a position longitudinally of the truck, a power unit, hydraulic pump means driven by said power unit, a drive wheel at each end of said pivoted drive axle, a variable displacement motor for each drive wheel, said outriggers being pivoted to the frame of the lift truck, hydraulic cylinders interposed between the frame and each outrigger to swing the outrigger from a storage position alongside of the lift truck frame to a position extending laterally of the lift truck frame, an outrigger control valve for said outrigger cylinders, a mast structure carried by said drive axle, a load platform mounted on said mast structure, hydraulic cylinder means for tilting the mast, hydraulic cylinder means for hoisting said load platform, a tilt-hoist valve for tilting and hoisting cylinders, a manually operated vehicle drive control valve, a displacement valve responsive to torque demand at the drive wheels to vary the displacement of the drive motors, a manually operable multi-phase valve to effect different phases of rotation of the drive motors for guiding the lift truck for stacking, conduit means connecting the output of the pump means to said tilthoist valve, conduit means connecting the output of said pump means to said outrigger control valve, conduit means to direct the carry-over of the output from the pump means to said vehicle drive control valve, and conduit means to direct hydraulic fluid from said tilt-hoist and outrigger valves to said drive motors through said drive control valve and through said multi-phase valve in the sequence named.

References Cited in the file of this patent UNITED STATES PATENTS 2,774,436 Ferris Dec. 18, 1956 2,789,648 Huffman Apr. 23, 1957 2,986,295 Shaffer May 30, 1961 

